The effect of saturation degree of methane hydrate on the shear strength of synthetic methane hydrate sediments

Shear strength of Toyoura sand containing methane hydrate synthesized in a tri-axial pressure vessel has been investigated. Saturation degree of methane hydrate in sand specimens was changed by initial water content as well as induction period of methane hydrate formation. The results from tri-axial compression tests employing two kinds of specimens, i.e. specimens with methane hydrate formed in ice-sand mixture(TYPEA) and/or in water-sand mixture(TYPE B), revealed the effects of methane hydrate saturation on shear strength and elastic properties including cohesion and internal friction angle. The proportional relationship between the shear strength and the methane hydrate saturation degree was obtained, however, existence of methane hydrate up to around 25% of the saturation degree for TYPE A showed little effect on the increase in shear strength. On the other hand, the shear strength for TYPE B exceeded that for TYPE A and the increase rate of the strength rose exponentially with saturation degree of methane hydrate. (Author)